A Versatile Scanning Photocurrent Mapping System to Characterize Optoelectronic Devices based on 2D Materials

The investigation of optoelectronic devices based on 2D materials and their heterostructures is a very active area of investigation with both fundamental and applied aspects involved. Here, a description of a home-built scanning photocurrent microscope is presented, which is designed and developed to perform electronic transport and optical measurements of 2D-materials-based devices. The complete system is rather inexpensive (<10 000 (sic)) and it can be easily replicated in any laboratory. To illustrate the setup, current-voltage characteristics are measured, in the dark and under global illumination, of an ultrathin p-n junction formed by the stacking of an n-doped few-layer MoS2 flake onto a p-type MoS2 flake. Scanning photocurrent maps are then acquired, and by mapping the short-circuit current generated in the device under local illumination, it is found that at zero bias, the photocurrent is generated mostly in the region of overlap between the n-type and p-type flakes.